A study has for the first time found high levels of tapeworm infection, potentially causing cognitive defects, among primary schoolchildren in rural mountainous areas.

Researchers in a joint study by Stanford University in the United States and Sichuan province health authority said that such infections made children highly vulnerable, with severe social consequences.

Neurological problems caused by the infections could lead to poor academic performance, dropping out of school and reinforcement the poverty cycle, it found.

“This disease invades the brain,” said John Openshaw, of Stanford School of Medicine and the study’s lead author. “Children who are affected during formative school years risk cognitive deficits which could enforce a cycle of poverty.”

The study, co-authored with researchers at Sichuan Centre for Disease Control and Prevention, assessed about 3,000 children in 27 schools for the tapeworm infection, by questionnaire and by analysing their blood samples in 2015. The children, aged mostly 11 to 13, were drawn from three counties at high altitude in western Sichuan province.

Their findings were published in international scientific journal PLOS Neglected Tropical Diseases last week.

The study focused on one type of tapeworm, taenia solium, whose eggs can be transmitted to humans by contaminated food, such as improperly cooked pork, water and close contact with a carrier.

The lava infects human intestines and releases thousands of eggs that pass through human faeces and are consumed by pigs, directly or through contaminated agricultural products.

Mature eggs, once hatched in the human body, migrate to tissues through the body including muscles and the central nervous system, causing seizure, loss of vision and hallucination.

The World Health Organisation estimates that the infection is one of the leading causes of epilepsy in the developing world and results in 29 per cent of epilepsy cases in endemic areas.

Although there have been epidemiological studies suggesting a high prevalence of tapeworm infection in rural China, the prevalence in children and its risk factors were unknown.

Researchers found that among the overall population prevalence of tapeworm infection was 6 per cent, but in some schools the rate rose to 15 per cent or higher.

The average prevalence of taenia solium infection in China was found to be 0.11 per cent. The estimated number of patients with taeniasis was 1.26 million, and the estimated number of cysticercosis cases was 3 million, according to the China Centre for Disease Control and Prevention.

The study identified schools as possible centres for transmission and said control measures in schools were important intervention tools.

“Schools represent large congregations of children, and risk for faecal-oral transmission and passage of eggs from tapeworm carriers is likely high,” researchers wrote.

“If this is the case, efforts to reduce school faecal-oral transmission may serve as a tool to interrupt disease transmission.”

China’s health authority has hastened the building of toilets in rural areas as part of a public health project since it started health care reform in 2009. By 2016, 80 per cent of toilets in rural areas had reached sanitary standard, it said.